1,934 research outputs found
Spatial information allows inference of the prevalence of direct cell-to-cell viral infection
The role of direct cell-to-cell spread in viral infections - where virions
spread between host and susceptible cells without needing to be secreted into
the extracellular environment - has come to be understood as essential to the
dynamics of medically significant viruses like hepatitis C and influenza.
Recent work in both the experimental and mathematical modelling literature has
attempted to quantify the prevalence of cell-to-cell infection compared to the
conventional free virus route using a variety of methods and experimental data.
However, estimates are subject to significant uncertainty and moreover rely on
data collected by inhibiting one mode of infection by either chemical or
physical factors. These methods assume that this inhibition process fully
eliminates its target mode of infection while exactly preserving the dynamics
of the other. In this work, we provide a framework for estimating the
prevalence of cell-to-cell infection from data which is experimentally
obtainable without the need for additional interventions, and two standard
mathematical models for viral dynamics with the two modes of infection. We
provide guidance for the design of relevant experiments and mathematical tools
for accurately inferring the prevalence of cell-to-cell infection
Multiplayer Cost Games with Simple Nash Equilibria
Multiplayer games with selfish agents naturally occur in the design of
distributed and embedded systems. As the goals of selfish agents are usually
neither equivalent nor antagonistic to each other, such games are non zero-sum
games. We study such games and show that a large class of these games,
including games where the individual objectives are mean- or discounted-payoff,
or quantitative reachability, and show that they do not only have a solution,
but a simple solution. We establish the existence of Nash equilibria that are
composed of k memoryless strategies for each agent in a setting with k agents,
one main and k-1 minor strategies. The main strategy describes what happens
when all agents comply, whereas the minor strategies ensure that all other
agents immediately start to co-operate against the agent who first deviates
from the plan. This simplicity is important, as rational agents are an
idealisation. Realistically, agents have to decide on their moves with very
limited resources, and complicated strategies that require exponential--or even
non-elementary--implementations cannot realistically be implemented. The
existence of simple strategies that we prove in this paper therefore holds a
promise of implementability.Comment: 23 page
Reservoirs of faecal indicator bacteria in well-head hand pumps in Bangladesh
The majority of the population of Bangladesh (90%) rely on untreated groundwater for drinking and domestic use. At the point of collection, 40% of these supplies are contaminated with faecal indicator bacteria (FIB). Recent studies have disproved the theory that latrines discharging to shallow aquifers are the major contributor to this contamination. In this study, we tested the hypothesis that hand pumps are a reservoir of FIB. We sampled the handle, spout, piston and seal from 19 wells in Araihazar Upazila, Bangladesh and identified that the spout and seal were reservoirs of FIB. These findings led to our recommendation that well spouts be regularly cleaned, including the removal of precipitated deposits, and that the seals be regularly changed. It is envisaged that one or both of these interventions will reduce the numbers of FIB in drinking water, thereby reducing the burden of diarrhoeal disease in Bangladesh
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Increasing influence of heat stress on French maize yields from the 1960s to the 2030s
Improved crop yield forecasts could enable more effective adaptation to climate variability and change. Here, we explore how to combine historical observations of crop yields and weather with climate model simulations to produce crop yield projections for decision relevant timescales. Firstly, the effects on historical crop yields of improved technology, precipitation and daily maximum temperatures are modelled empirically, accounting for a nonlinear technology trend and interactions between temperature and precipitation, and applied specifically for a case study of maize in France. The relative importance of precipitation variability for maize yields in France has decreased significantly since the 1960s, likely due to increased irrigation. In addition, heat stress is found to be as important for yield as precipitation since around 2000. A significant reduction in maize yield is found for each day with a maximum temperature above 32 °C, in broad agreement with previous estimates. The recent increase in such hot days has likely contributed to the observed yield stagnation. Furthermore, a general method for producing near-term crop yield projections, based on climate model simulations, is developed and utilized. We use projections of future daily maximum temperatures to assess the likely change in yields due to variations in climate. Importantly, we calibrate the climate model projections using observed data to ensure both reliable temperature mean and daily variability characteristics, and demonstrate that these methods work using retrospective predictions. We conclude that, to offset the projected increased daily maximum temperatures over France, improved technology will need to increase base level yields by 12% to be confident about maintaining current levels of yield for the period 2016–2035; the current rate of yield technology increase is not sufficient to meet this target
Sixteen years of Collaborative Learning through Active Sense-making in Physics (CLASP) at UC Davis
This paper describes our large reformed introductory physics course at UC
Davis, which bioscience students have been taking since 1996. The central
feature of this course is a focus on sense-making by the students during the
five hours per week discussion/labs in which the students take part in
activities emphasizing peer-peer discussions, argumentation, and presentations
of ideas. The course differs in many fundamental ways from traditionally taught
introductory physics courses. After discussing the unique features of CLASP and
its implementation at UC Davis, various student outcome measures are presented
showing increased performance by students who took the CLASP course compared to
students who took a traditionally taught introductory physics course. Measures
we use include upper-division GPAs, MCAT scores, FCI gains, and MPEX-II scores.Comment: Also submitted to American Journal of Physic
Decision Problems for Nash Equilibria in Stochastic Games
We analyse the computational complexity of finding Nash equilibria in
stochastic multiplayer games with -regular objectives. While the
existence of an equilibrium whose payoff falls into a certain interval may be
undecidable, we single out several decidable restrictions of the problem.
First, restricting the search space to stationary, or pure stationary,
equilibria results in problems that are typically contained in PSPACE and NP,
respectively. Second, we show that the existence of an equilibrium with a
binary payoff (i.e. an equilibrium where each player either wins or loses with
probability 1) is decidable. We also establish that the existence of a Nash
equilibrium with a certain binary payoff entails the existence of an
equilibrium with the same payoff in pure, finite-state strategies.Comment: 22 pages, revised versio
The Grizzly, October 1, 2015
Safety First: New Campus Safety Officer Looks to Connect with Students • Artist Transforms Ursinus Faces into Famous Painting • Design Philly Festival Kicks Off with Pop-up Exhibition • Politics Professor Looks to Expand Research on Africa • U-Imagine Center Promotes Entrepreneurship • UC Students Get Down to the Heart of the Matter • Putting Passion into Practice • Opinions: Is Fun Home Appropriate for CIE?; The Cleaning Staff Should Not be Ignored • In the Swing of Things • Men\u27s and Women\u27s Rugby Teams Prepare for Seasonhttps://digitalcommons.ursinus.edu/grizzlynews/1672/thumbnail.jp
The Grizzly, November 12, 2015
Highlighting a New Trend on Campus • Making Connections: Ursinus Prepares to Break Ground on a Structure Between Pfahler and Thomas • Acclaimed Literary Critic to Give Talk on Campus • Ursinus Brings Top Lawyer Aboard in New Position • International Perspective: How One Student Uses Dance to Connect Ethiopia and Ursinus • Can You Really Netflix and Chill Without Killing Your Grades? • Opinions: Are You a White Feminist?; Bridge of Spies • Defensive Lineman Unleashes Passion for Music • Field Hockey Upsets F&M for Titlehttps://digitalcommons.ursinus.edu/grizzlynews/1677/thumbnail.jp
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